Heart valve surgery. Surgeon's hand holding an inflated balloon catheter for use during heart valve surgery. Soft-tissue retractors hold open a small hole in the patient's chest (lower centre). The balloon will be deflated and a catheter (thin tube) will guide it through the patient's groin artery and up to the heart. The balloon will be inflated just ouside the heart (in the aorta) to block the blood flow and allow a heart-lung machine to take over from the heart. This then allows surgery through the hole (between two ribs) to replace the defective heart valve. Such keyhole heart surgery is less traumatic than open heart surgery (where the rib cage is opened).